build: update golang version to 1.20

[0Tech]

Description

Closes: #664

[codecov[bot]]

Codecov Report

Merging #665 (1c50c4a) into main (1cab268) will decrease coverage by 0.08%. The diff coverage is 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #665 +/- ## ========================================== - Coverage 66.51% 66.43% -0.08% ========================================== Files 283 283 Lines 37818 37821 +3 ========================================== - Hits 25155 25128 -27 - Misses 10868 10889 +21 - Partials 1795 1804 +9 ``` | [Files Changed](https://app.codecov.io/gh/Finschia/ostracon/pull/665?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia) | Coverage Δ | | |---|---|---| | [rpc/core/routes.go](https://app.codecov.io/gh/Finschia/ostracon/pull/665?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-cnBjL2NvcmUvcm91dGVzLmdv) | `0.00% <ø> (ø)` | | | [rpc/jsonrpc/server/http\_server.go](https://app.codecov.io/gh/Finschia/ostracon/pull/665?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-cnBjL2pzb25ycGMvc2VydmVyL2h0dHBfc2VydmVyLmdv) | `89.61% <100.00%> (ø)` | | | [rpc/jsonrpc/server/ws\_handler.go](https://app.codecov.io/gh/Finschia/ostracon/pull/665?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia#diff-cnBjL2pzb25ycGMvc2VydmVyL3dzX2hhbmRsZXIuZ28=) | `35.71% <100.00%> (+0.77%)` | :arrow_up: | ... and [12 files with indirect coverage changes](https://app.codecov.io/gh/Finschia/ostracon/pull/665/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Finschia)

[ulbqb]

Please update these files. https://github.com/Finschia/ostracon/blob/80d5dd0b2dd56f31befafa9190b706944e5224f1/README.md?plain=1#L9 https://github.com/Finschia/ostracon/blob/80d5dd0b2dd56f31befafa9190b706944e5224f1/Makefile#L261 https://github.com/Finschia/ostracon/blob/80d5dd0b2dd56f31befafa9190b706944e5224f1/test/e2e/docker/Dockerfile#L10